1. Field of the Invention
The present invention relates to a laminated substrate for a window; a laminated substrate for a window with a frame body; an automobile with a laminated substrate for a window; and an intermediate layer structure for a laminated substrate for a window.
2. Description of the Related Art
In recent years, as weight of a vehicle has been reduced, it has been considered to use, as a glass plate for a window glass that has been used so far, a thinner and lighter glass plate. However, as a plate thickness of the glass plate is reduced, a problem arises such that a sound insulating property is lowered.
For example, in Patent Document 1 (WO 2012/141002), it has been proposed to use a laminated glass as a glass plate for a window glass, and to use a film with a sound insulating property as an intermediate film (which is also referred to as the “sound insulating intermediate film,” hereinafter), so as to solve the problem that the sound insulating property is lowered.
Specifically, by providing a sound insulating intermediate film with small shear modulus between two glass plates, vibration transmitted from one glass plate to the other glass plate can be absorbed; and vibrations of the two glass plates can be caused to interfere with each other by generating a phase shift between the vibrations of the two glass plates. As a result of these, vibration of the laminated glass plate is suppressed, and a sound insulating property is obtained.
However, for the laminated glass for which the sound insulating intermediate film is used, as in Patent Document 1, stiffness is lowered, compared to a glass plate formed of a single plate having a thickness that is the same as that of the laminated glass. For example, when a glass plate that is a single plate having a plate thickness of 5 mm is compared with a laminated glass in which two glass plates, each of which has a plate thickness of 2.5 mm, are combined, the stiffness of the laminated glass is approximately a half of that of the glass plate that is the single plate.
As a cause of lowering the stiffness of the laminated glass relative to that of the glass plate that is the single plate, it can be considered that, since the shear modulus is small not only for dynamic force, such as a sound wave, but also for static force of which the frequency is smaller than that of the sound wave, upon static force being generated in the laminated glass, the two glass plates are individually deformed.
Namely, it is preferable that the shear modulus of the intermediate film be small, so that the sufficient sound insulating property is obtained, as described above; however, the sound insulating property and the stiffness are in a trade-off relationship such that, when the shear modulus is small, the stiffness against static force is lowered, so that it is difficult to achieve both of them.
Here, the problem that it is difficult to achieve both the sound insulating property and stiffness can arise not only for the laminated glass, but also for a case of, for example, a laminated body where the two glass plates are replaced with resin plates.
There is a need for a laminated substrate for a window; a laminated substrate for a window with a frame body; an automobile with a laminated substrate for a window; and an intermediate layer structure for a laminated substrate for a window, with which a sufficient sound insulating property is obtained, and sufficient stiffness is obtained.